Cutting fluids can improve the performance of metal cutting tools by cooling both the cutting tool and the workpiece, by lubricating the cutting and non-cutting surfaces on the tool, by inhibiting seizure between the chip and the tool, and by flushing the chips from the work area. The benefits of using cutting fluid can be a lowered tool force, improved tool life or a faster cutting speed, improved surface finish on the machined surface and better control on the accuracy of machined dimensions. Cutting fluids are also used on grinding operations to cool the workpiece and improve the surface finish. Rust prevention on machined surfaces is another important cutting oil contribution.
Water-base soluble or emulsifying oils are sometimes classified as aqueous cutting fluids. These fluids are commonly a mixture of mineral oil with an emulsifying agent and may include corrosion and fungi inhibitors along with bactericides and other specialized additives. When such oils are mixed with water, an emulsion is formed rather than a solution, but the term "soluble oil" has been generally accepted. Depending upon the application, these oils are mixed with water in concentrations ranging from five to seventy parts of water to one part of oil. Soluble or emulsifying oils are very effective coolants and are considered as inexpensive, general-purpose cutting fluids for almost all machining and grinding operations.
Chemical or synthetic cutting fluids is true solutions of organic and inorganic materials in water, with little or no petroleum product content. These chemical or synthetic fluids may include added lubricants and wetting agents or such additives may be omitted. Chemical cutting fluids containing lubricants and wetting agents are recommended for use on tough machining operations such as tapping, sawing, broaching, gear shaving and gear cutting as well as turning, milling and drilling. They are excellent rust inhibitors and have high heat conductivity but have a tendency to foam in some applications.
Chemical cutting fluids which do not contain lubricants or wetting agents are clear solutions which do not foam readily and are also excellent coolants and rust inhibitors. They are recommended for surface grinding but not for severe machining operations where their lack of lubricity is a disadvantage. Such solutions have a significant advantage in resisting the growth of undesirable bacteria.
The growth of bacteria is a common problem with cutting fluids and if unchecked, will lead to the deterioration of cutting fluid performance. So called "tramp oil", from machine tool lubricants, the parts being machined and other sources contaminates the cutting fluid over a period of time. This not only brings more undesirable anaerobic bacteria into the fluid but, the tramp oil also provides nutrients and a breeding ground for the bacteria. As a result, bacteria colonies tend to form where tramp oils collect. In a stagnant situation, the bacteria waste materials also interact with the tramp oil and cutting fluid to form gelatinous matter, which tends to clog the cutting fluid circulation system. Maintaining constant circulation and or agitating cutting oils tends to prevent the formation of colonies and aeration tends to discourage bacteria growth. Tramp oil rises to the top since it is lighter than the aqueous cutting fluids and it is desirable to make a practice of periodically skimming it off to diminish the contamination potential.
It is particularly desirable to extend the useful life of cutting fluids inasmuch as most of these products are hazardous wastes under prevailing EPA guidelines and as such, require expensive disposal measures.
Therefore, the first object of the present invention is to provide an improved method and apparatus for maintaining the condition of the cutting oil supply of a machine tool. A second object is that this improved apparatus should provide simultaneous operation of the cutting fluid circulation pump, cutting fluid aeration and tramp oil separation. A third object is to provide this improved apparatus in a form that is inexpensively made and readily installed as an accessory on virtually any machine tool.